Associations of Interdecadal/Interannual Climate Variability and Long-Term Colorado River Basin Streamflow

Janak Timilsena, University of Nevada, Las Vegas
Thomas C. Piechota, University of Nevada, Las Vegas
Glenn A. Tootle, University of Tennessee - Knoxville
Ashok Singh, University of Nevada - Las Vegas


The study presented here utilized long-term streamflow records (over 500 years) to investigate the influence of interannual/interdecadal climate variability on the Colorado River basin. 19 unimpaired water year streamflow stations were reconstructed utilizing partial least square regression using standard tree ring chronologies. The spatial and temporal variability of drought was evaluated for all the stations for the different centuries in the record. Finally, the relationship between individual impact of ENSO, PDO, and AMO and its combined effect on streamflow was determined using the non parametric Rank Sum test for different lag years (0, +1, +2, and +3) of streamflow. This research also determined the change in streamflow volume with respect to the long-term mean volume of the basin due to individual and coupled effect of oceanic climate influences. Results indicate that there is an increase in streamflow during El Niño and decreased streamflow during La Niña in the basin. Similarly, PDO warm/cold resulted in increased/decreased streamflow. There were few stations related to the AMO in the basin. Finally, the differences in the Upper and Lower basin were noted in the magnitude of changes in streamflow (in terms of percentage) under different individual and coupled influences of ENSO, PDO, and AMO.